A method of producing polyethylene

 

(57) Abstract:

The invention relates to a method for producing polyethylene by the method of radical polymerization under high pressure and can be used in the chemical and petrochemical industries. A method of producing polyethylene is carried out in mass in one zone autoclave reactor with a mixing device at an elevated temperature to initiate reaction of organic peroxides, supporting the difference between the minimum temperature value in the upper part of the reactor and the maximum value of the temperature in the lower part of the reactor in the range of 40-70oWith, in the upper part of the reactor set minimum temperature 215-240oWith, and in the lower part of the reactor maximum temperature 260-290oWith the top and bottom of the reactor serves the solutions of organic peroxides or solutions of mixtures of organic peroxides with these temperatures the value of the works of the rate constants for the decay of individual peroxide or additive constants of the decay rate of the mixture of peroxides during their stay at the top or bottom parts of the reactor, equal 16-240. Technical result: high conversion of ethylene, with lagerweij substances in the polyethylene.

The invention relates to the technology of production of polyethylene by the method of radical polymerization under high pressure and can be used in the chemical and petrochemical industries. Known (Patent RF N1838330, MKI6C 08 F 110/02, publ. 30.08.93 g) the method of producing polyethylene, comprising the polymerization of ethylene in dual-zone autoclave reactor with a stirrer, the reaction space of which is divided by a partition wall (baffle) into two zones: the upper zone, covering 56% of the volume, and the lower zone, comprising 46% of the volume (see example 3 for comparison and examples 6, 7). The polymerization process leading to mass at a pressure 135-227 MPa with the introduction of n-paraffins (Parex) in the presence of radical initiators are organic peroxides, which are used, for example, tert-butyl peroxypivalate, served with solvent (Parex or paraffin oil) in a stream of ethylene in the upper zone of the reactor, and di-tertbutylphenol supplied with the solvent in the bottom zone of the reactor. When using these peroxides temperature in the upper zone of the reactor support equal C (172oC) at the top of the zone and 470K (197oC) at the bottom of the zone (the average temperature of the reaction mixture in the area is 185oC). In nijnatten the temperature in the area is 251oC). The temperature difference in the upper zone of the reactor is 25oC, in the bottom 38oC, i.e. the temperature difference in each of the zones is less than 40oC., the polymerization Process is carried out in the presence of agents, chain transfer, which are mainly used Propionaldehyde, methyl ethyl ketone. The resulting polyethylene and unreacted ethylene is directed through the control valve in the system two-stage separation of the polyethylene from the unreacted reaction mixture. The polyethylene is removed from the system recyclo through the discharge extruder and transferred to the granulate, and unreacted ethylene after cleaning and cooling is mixed with the original ethylene and sent to the reactor.

The described method provides high conversion of ethylene, for example, upon receipt of high-viscosity polyethylene with a melt flow index of 0.3 g/10 min, the conversion reaches 17.5% in terms of the initial ethylene. The polyethylene obtained by this method has a sufficiently high uniformity and purity, contains almost no gel-like inclusions, which is an important positive factor in the production of the film.

The disadvantages of this process are:

1. Increased consumption of depolimerization in the upper zone of the reactor (172-197oC). According to our data, the consumption of peroxides is 0,0051 mol per kg of polyethylene and, as a consequence, increased (to 0.69 wt.%) content in the polymer extractables (see our reference example 16).

2. Long stay (63) in the reactor of a significant amount (50 wt. %) of ethylene, which reduces the performance of the installation. The residence time of the ethylene in the reactor is calculated on the basis specified in examples 3, 6, 7 RF patent N 1838330 reactor volume, the volumes of the upper and lower zones of the reactor, the quantities supplied to each zone of ethylene, using published data on the density of the ethylene in the synthesis parameters in each zone of the reactor.

3. A rather complex control process associated with the need to maintain strict temperature in each zone of the reactor.

Closest to the claimed method according to essential features and the achieved effect is a method of producing polyethylene described in the book "high-pressure Polyethylene. Scientific and technical basis for industrial synthesis. (A. C. Polyakov, F. I. Duntov, A. E. Sofiev etc. - L., Chemistry, 1988, S. 27-37). In accordance with this method, the polyethylene produced by polymerization of ethylene in merchanidise peroxides at a pressure of 150-250 MPa and high temperature. Ethylene and solutions of peroxides in organic solvent fed into the reactor at one or more points along the height of the reactor at the top and bottom of the reactor. The residence time of the reaction mixture in the autoclave reactor 10-120 C. the resulting polyethylene is separated from the unreacted reaction mixture in systems recyclo high and low pressures. The polyethylene is removed from the system recyclo through the discharge extruder and transferred to the granulate, and unreacted ethylene after cleaning and cooling is mixed with the original ethylene and fed into the reactor.

As the organic peroxides used di-tert-butylperoxide, tert-butyl peroxybenzoate, di-laurelbrooke peroxide fractions of fatty acids and other compounds easily undergo homolytic decomposition with the formation of free radicals.

Are listed in the book "high density Polyethylene" S. 29 the temperature of the polymerization 170-280oC is common for single-band and dual-zone autoclave reactor. As indicated there, on the S. 29, 30, autoclave reactors as in the single-band and multi-zone, it is necessary to maintain the temperature difference across the height of the reactor in a narrow range. The temperature difference across the heights of the technical basis for industrial synthesis. A. C. Polyakov, F. I. Duntov, A. E. Sofiev etc. - L., Chemistry, 1988, S. 30, Fig. 2.14). When this difference in one zone of the reactor, the polymerization temperature must be within 215-280oC. If the initial temperature of polymerization below 215oC is formed polyethylene with a very low (less than 0.3 g/10 min) melt flow index, unsuitable for processing into film and pipe; when the maximum temperature in the lower part of the reactor over 280oC is formed polyethylene with a melt flow index of more than 7 g/10 min, not find wide practical application.

The manufacturing process of polyethylene, implemented in accordance with the described method of the prototype, more manageable than the polymerization of ethylene in a 2-3-zone reactor, but it is characterized by the following disadvantages:

1. Low conversion of ethylene, especially when getting polyethylene with a melt flow index in the range of 0.3 to 2.0 g/10 min. This is because to obtain a polyethylene with a melt flow index of 0.3 and 2.0 g/10 min requires a minimum temperature of polymerization in the upper part of one zone of the reactor was 215-218oC and 225-228oC, respectively. In connection with the need to maintain the RA should not exceed 258oC and 268oC, respectively. Given that it is well known (see kN. Technology for the production of polyethylene and polypropylene. Votes A. P., Dances A. I., M., Chemistry; 1978, S. 52), increasing the conversion rate of ethylene 0.07 wt.% with increasing temperature difference on the 1oC between the temperature of the ethylene feedstock, which is usually ~45oC, and the temperature of the reaction mixture at the reactor exit, the maximum possible conversion of ethylene upon receipt of polyethylene with a melt flow index of 0.3 g/10 min 16.4 wt.%, but when polyethylene with a melt flow index of 2 g/10 min and 17.1 wt.% (see our test cases 17 and 18).

The maximum possible (18.3 wt.%) the conversion of ethylene in one zone autoclave reactor is achieved at the maximum possible temperature in the lower part of the reactor 280oC. However, this process produces polyethylene with a melt flow index of more than 7 g/10 min as the temperature in the upper part of the reactor should not be less than 240oC.

2. High consumption of peroxides and related high content in polyethylene extractables. High consumption of peroxides due to the current lack of selection criteria for prinny mode and during their stay in the reactor. An indirect confirmation of the above is the high content of extractable substances in the polyethylene obtained by the method prototype. So by the standards of GOST 16337-77 (table 5), the polyethylene produced in the reactor pressure type (a list of these polyethylene grades given in the book. "High density polyethylene", 180 C.), the content of extractable substances in the polyethylene of the highest grade can reach 0.9 to 1.4 wt.%.

The technical result, which provides the inventive method, is to increase the conversion of ethylene, especially when getting polyethylene with a melt flow index of 0.3 to 2 g/10 min, the reduction of peroxides and related improvement of the quality of the polyethylene by reducing it extractables.

This technical result is achieved due to the fact that in the method of producing polyethylene by polymerization of ethylene in weight in one zone autoclave reactor with a mixing device at an elevated temperature, pressure 130-250 MPa and residence time of the ethylene in the reactor 10-50 with initiating the polymerization reaction of organic peroxides, supplied in the form of solutions in organic solvents at the top and the necks of the reaction mixture in systems recyclo high and low pressure, in the polymerization process support the difference between the minimum temperature value in the upper part of the reactor and the maximum value of the temperature in the lower part of the reactor in the range of 40-70oC, in the upper part of the reactor to maintain a minimum temperature 215-240oC, and in the lower part of the reactor maximum temperature 260-290oC, in the upper and lower part of the reactor serves the solutions of organic peroxides or solutions of mixtures of organic peroxides with these temperatures the value of the works of the rate constants for the decay of individual peroxide or additive constants of the decay rate of the mixture of peroxides during their stay at the top or bottom parts of the reactor, equal 16-240.

As mentioned above, at present, it is generally understood that in one zone autoclave reactor (especially in the reactor with a small length of the reactor to its diameter) temperature gradient along the height of the reactor should be small (less than 40oC). This view is driven by considerations on the stability of the polymerization process, as it is believed that a significant temperature gradient along the height of the reactor can lead to thermal decomposition reacts ascioti the polymerization process can be ensured, and when the temperature difference across the height of the reactor in the range of 40-70oC even when using a stirrer having a relatively low speed (1000 rpm) by maintaining in one zone autoclave reactor relevant temperature regime: a relatively low temperature in the upper part of the reactor (215-240oC) and high in the lower part of the reactor (260-290oC). Specified temperature in the upper and lower parts of the reactor create by filing solutions selected individual organic peroxides or mixtures thereof in the corresponding points of the reactor. The authors found that a sufficient depth of decomposition of peroxide (or a mixture of peroxides) is achieved when the value of the works of the rate constants for the decay of individual peroxide (Kior constant decomposition rate (Ksmfor mixtures of peroxides at specified temperatures during their stay at the top or bottom parts of the reactor, equal 16-240. If the product of the rate constants of the decay of individual peroxide (or a mixture of peroxides) during his stay at the top or bottom parts of the reactor exceeds the authors found the value of the upper limit (240), it leads to increase of consumption of peroxides per unit of produced polyethylene, reduced the state of Thuringia substances (see our counter. Ave N 12); if this product is less than the lower limit (16), due to incomplete decomposition of peroxide in the reactor, the latter enters the system branch of the polyethylene from the unreacted ethylene and causes thermal explosive decomposition of ethylene (see our counter. Ave N 13).

To calculate the rate constants of decomposition of a mixture of peroxides (Ksm) use the rule of additivity, i.e.

Ksm= K1C1+ K2C2,

where K1and K2individual rate constants of decomposition of peroxides 1 and 2, respectively, at this temperature;

C1and C2- mass fraction of peroxides 1 and 2.

Individual rate constants of the decay Kidetermined by known (see the book "high-pressure Polyethylene. Scientific and technical basis for the industrial synthesis" /Century A. Polyakov, F. I. Duntov, A. E. Sofiev etc. - L.: Chemistry, 1988, S. 55) equation

Ki= 0,693/t1/2,

wheret1/2- half-life - the time at which the peroxide concentration at a given temperature is reduced by half.

Found by the inventors of the empirical correlation makes it possible to maintain the temperature difference across the height of the reactor 40-7 is eroxide, to increase the conversion rate of ethylene and reduce the content of extractable substances in the resulting polyethylene, which improves the conditions of its processing into products and expands the scope of products.

When implementing the proposed method as peroxides for the upper part of the reactor can be used, for example, tert-butyl peroxy-3,5,5-trimethylhexanoate, tert-butyl peroxybenzoate, tert-butyl peroxyacetate, 2,2-di-tert-butylperoxide, 1,1-di-tert-butylperoxycyclohexyl or mixtures thereof; and the lower part of the reactor - di-tert-butylperoxide, tert-butylcumylperoxide, di-semiprocessed, di-tert-butyl peroxybenzoate, and mixtures thereof.

The solvent peroxides, it is advisable to use a relatively low molecular weight acyclic compounds (normal, isotrate), with the number of carbon atoms in the molecule is from 10 to 20, in particular Dean, pentadecane, alcosan, isododecane, isohexadecane or mixtures thereof.

If necessary, to modify the properties of the polyethylene in the reaction mixture can be introduced agents, chain transfer, such as propane, propylene, isopropyl alcohol, etc.

Obtained in accordance with the proposed method, the polyethylene can be used in PR is x products fittings and other products.

The invention is illustrated by the following examples.

Example 1.

In the experience of using one zone autoclave reactor continuous volume of 250 l, the reaction space which can be divided into two parts: upper and lower, the ratio of the volumes of the upper and lower parts is 1:1. The reactor is equipped with a high-speed stirrer, rotational speed is 1000 rpm. For measuring the temperature in the reactor using four thermocouples, two of which are located in the upper part of the reactor, and two at the bottom. Thermocouples installed in such a way that they fix the values of the temperature of the reaction mixture entering and leaving the upper and lower parts of the reactor. The temperature of the external wall of the reactor, 170oC support the cold air.

In reactor three threads continuously served 12000 kg/h of ethylene with temperature 45oC under the pressure of 148 MPa. One stream of ethylene in a quantity of 500 kg/h is fed through a mounted above the reaction space of the motor housing in the upper part of the reactor. The second stream of ethylene in the number of 5500 kg/h is injected together with the initiator solution into the upper part of the reactor opposite anoeta, 6 wt. % of tertBUTYLPEROXY (the ratio of peroxides 40: 60) and 90 wt.% acyclic solvent, which is used as isododecane.

The amount of the initiator mixture for the top of the reactor govern according to the testimony of the first thermocouple, supporting the flow initiator mixture, the temperature of the reaction mixture in the first measuring point 225oC. In the second probe set temperature 249-250oC. the Average temperature in the upper part of the reactor is 237oC, the residence time of the mixture of peroxides in the upper - 33 C. the Additive value of the rate constant of the decomposition of this mixture of peroxides 237oC = 7.5/s, the product of the additive values of the rate constants for the decomposition of a mixture of initiators during her stay in the upper part of the reactor is 240. The third stream of ethylene in the amount of 6000 kg/h served in the lower part of the reactor opposite the third thermocouple. Before entering the reactor in a stream of ethylene injected a solution of the initiator mixture, consisting of a 3.5 wt. % di-tert-butylperoxide and 96.5 wt.% solvent - isododecane. The amount of feed in the lower part of the initiator mixture govern according to the testimony of the fourth thermocouple. On the fourth thermocouple support TV lower part of the reactor is equal to 261oC. the rate Constant for the decomposition of di-tert-butylperoxide - 8,3/s, the residence time of the peroxide in the lower part of the reactor 13, the product of the rate constants of decomposition of di-tert-butylperoxide during his stay in the lower part of the reactor is equal to 110. The difference in temperature between a minimum temperature value in the upper part of the reactor and the maximum value of temperature in the lower part of the 50oC, the maximum residence time of the ethylene in the reactor 46, the conversion of the original ethylene - 18,1%, the total flow of peroxides - 0,0017 mol per kg of polyethylene.

From the reactor the resulting polyethylene and unreacted reaction mixture is sent through a throttling valve on a two-stage separation of the polymer from the unreacted reaction mixture in the system recyclo high and low pressures. In recycling high pressure support pressure of 25 MPa, recycling low pressure of 0.13 MPa. The molten polyethylene with a temperature of 255oC of the separator high pressure fed into the separator low pressure and then to a discharge extruder, and formed in the separators solution of ethylene to low molecular weight products are cooled, cleaned and served on mixed with fresh ethylene. Performance is i.i.d. according to GOST 16337-77:

1. The melt flow index at 190oC - 2 g/10 min.

2. The number of inclusions, PCs - 0.

3. Mass fraction of extractables, % - 0,41.

Example 2.

The experience is conducted under the conditions of example 1, but the temperature difference across the height of the reactor support equal to 70oC, while the temperature of the polymerization reaction in the upper part of the reactor, measured by the first thermocouple is 220oC, the second thermocouple - 251oC, as the initiator fed to the upper part of the reactor, using 10 wt.% solution mixture of peroxides, tert-butyl peroxy-3,5,5-trimethylhexanoate and tert-butyl peroxybenzoate, taken in the ratio 1:1. The average temperature in the upper part of the reactor is 235oC, the additive constant is the decay rate of the mixture of peroxides at this temperature - 6,2/s, the product of the rate constants of decomposition of peroxides during their stay in the upper part of the reactor is 200. The temperature in the lower part of the reactor opposite the third thermocouple support 255oC, at the outlet of the reactor (the fourth thermocouple) - 290oC, average temperature in the lower part of the reactor is 272oC. the rate Constant of decay of di-tert-BUTYLPEROXY the s - 11, the product of the rate constants of decomposition of di-tert-butylperoxide during his stay at the bottom of the reactor 91,0. As a solvent of the peroxides used for both the upper and lower part of the reactor used, eicosan. Conversion of the ethylene feedstock amounts to 19.4 wt.%, the maximum residence time of the ethylene in the reactor 44, the total flow of the initiators - 0,0016 mol per kg of the obtained polyethylene. Polyethylene has the following properties:

1. The melt flow index of 2.8 g/10 min.

2. The number of inclusions, PCs - 0.

3. Mass fraction of extractables, % - 0,43.

Example 3.

The experience is conducted under the conditions of example 1, but the total amount fed to the reactor ethylene is 16000 kg/h, of which 8000 kg/h fed into the top of the upper part of the reactor, including 500 kg/h engine reactor and 8000 kg/h (third stream) in the top of the lower part of the reactor. The temperature difference across the height of the reactor between the first and fourth thermocouples 40oC, while the temperature of the polymerization reaction in the upper part of the reactor, measured by the first thermocouple, equal to 215oC, the second thermocouple - 247oC, as the initiator fed to the upper part of the reactor, ispolzovat, dissolved in 90 wt.% isododecane. The average temperature in the upper part of the reactor 231oC, the additive constant is the decay rate of the mixture of peroxides - 4,6/s, the time of their stay - 25, a product of the additive constants of the decay rate of the mixture of peroxides during their stay in the upper part of the reactor is equal to 110. In the lower part of the reactor supports the following temperature range: temperature opposite the third thermocouple 238-239oC, opposite the fourth - 255oC, average temperature - 247oC. To maintain such a regime in the lower part of the reactor serves 10 wt.% a solution of tert-butyl peroxybenzoate in isododecane. The rate constant of decay of tertBUTYLPEROXY at 247oC - 13,0/s, the residence time of tert-butylperbenzoate at the bottom of the reactor 10, the product gives a value of 130. Conversion of the ethylene feedstock in the experience is 16.5%, the maximum residence time in the reactor - 47, the total flow of peroxides in the experience 0,0017 mol per kg of the obtained polyethylene. Polyethylene has the following properties:

1. The melt flow index of 0.5 g/10 min.

2. The number of inclusions, PCs - 0.

3. Mass fraction of extractables, % - 0,45.

Example 4.

Experience conducting Wei is 40oC, while the temperature of the polymerization reaction in the upper part of the reactor, measured by the first thermocouple is 240oC, the second thermocouple - 256oC, as the initiator fed to the upper part of the reactor, a mixture of peroxides consisting of 6 wt.% di-tert-butylperoxide and 4 wt.% tert-butyl peroxybenzoate, dissolved in 90 wt.% isododecane. The average temperature in the upper part of the reactor 248oC, the additive constant is the decay rate of this mixture of peroxides - 6,7/s, the product of the rate constants of decomposition of peroxides during their stay in the upper part of the reactor is equal to 220. In the lower part of the reactor together with ethylene enter the initiator solution consisting of 3.5 wt.% di-tert-butylperoxide and 96.5 wt.% solvent-isododecane. On the third probe set temperature 248-249oC, the fourth - 280oC. the Average temperature in the lower part of the reactor is equal to 264oC, the rate constant of the decomposition of di-tert-butylperoxide at this temperature - 5,0/s, the residence time of lead in the bottom of the reactor 13, the product of the rate constant of decay of di-tertBUTYLPEROXY during his stay in the lower part of the reactor is equal to 65. The conversion of ethylene is 18.5%, max is etilene. Polyethylene has the following properties:

1. The melt flow index is 7.0 g/10 min.

2. The number of inclusions, PCs - 0.

3. Mass fraction of extractables, % - 0,45.

Example 5.

The experience is conducted under the conditions of example 1, but the polymerization of ethylene is carried out at a pressure of 130 MPa and a temperature difference between the first and fourth thermocouples 45oC, the temperature of the reaction mixture in front of the first thermocouple is 215oC, opposite the second thermocouple is 247-248oC, average temperature in the upper part of the reactor is equal to 231oC. Formulation of the initiator solution to the upper part of the reactor the mixture of peroxides consisting of 5.6 wt.% tert-butyl peroxybenzoate and 4.4 wt. % tert-butyl peroxy-3,5,5 - trimethylhexanoate, the rest (90 wt. %) - isododecane. The residence time of the mixture of initiators in the upper part of the reactor is 33, the additive value of the rate constant of the decomposition of this mixture of initiators is 4.7/s, the product of the additive values of the rate constants for the decomposition of a mixture of initiators during her stay in the upper part of the reactor is 150. The temperature in the lower part of the reactor opposite the third thermocouples installed within 249-250oC, opposite the fourth polymerizatio in the lower part of the reactor initiating use the following mixture: 4 wt.% tert-peroxyacetate, 6 wt.% di-tert-butylperoxide and 90 wt.% isododecane. Stay peroxides in the lower part of the reactor 14, the additive value of the rate constant of the decomposition of the initiators and 12.4/s, the product of these values is equal to 170. Conversion of fresh ethylene in the experience is of 16.6%, the maximum residence time of the ethylene in the reactor 47, the total flow of the initiators 0,0018 mol per kg of polyethylene. Polyethylene has the following properties:

1. The melt flow index of 1.5 g/10 min.

2. The number of inclusions, PCs - 0.

3. Mass fraction of extractables, % - 0,42.

Example 6.

Experience are in one zone autoclave reactor with a volume of 3 l equipped with a high-speed stirrer rotating at a speed of 1500 rpm and two thermocouples installed in the upper and lower parts of the reactor. Ethylene containing as an agent of chain transfer to 0.3 wt.% propane, in the amount of 550 kg/h under a pressure of 250 MPa fed into the reactor in two streams: one of them (60 kg/h) is sent to the engine of the reactor, and the second main flow directly into the upper part of the reactor opposite the top thermocouple. Filing initiating solutions is carried out in two points: one solution in the main stream of ethylene before entry into the reactor, and brownie the polymerization reaction in the upper part of the reactor spend 10 wt. % solution of a mixture of peroxides consisting of 5.6 wt.% tert-butyl peroxybenzoate and 4.4 wt.% tertBUTYLPEROXY-3,5,5-trimethylhexanoate, the rest (90 wt. %) - isododecane. The temperature of the reaction mixture in the upper part of the reactor support equal 226oC, the residence time of the mixture of peroxides ~5 C. the Additive constant is the decay rate of this mixture of peroxides at 226oC - 3,3/s, the product of the rate constants of decomposition of a mixture of initiators during their stay in the upper part of the reactor is 16. In the lower part of the reactor serves 5 wt.%-s ' solution of di-tert-butylperoxide in isododecane, the temperature of the reaction mixture in the lower part of the reactor support 270oC (the temperature difference across the height of the reactor is ~44oC). The rate constant of the decomposition of di-tert-butylperoxide at a temperature of 270oC is equal to 7.3, during his stay in the lower part of the reactor 5 (total residence time of the reaction mixture in reactor 10 (C), the product of the rate constants of decomposition of di-tert-butylperoxide during his stay at the bottom of the reactor 36. Conversion of fresh ethylene is 17.4 per cent, the total flow of the initiators 0,0017 mol per kg of polyethylene. The separation of the obtained polyethylene from the unreacted reaction the allocation of polyethylene through the extruder and the return of ethylene synthesis system. Get 96 kg/h of polyethylene with the following properties:

1. The melt flow index of 0.3 g/10 min.

2. The number of inclusions, PCs - 0.

3. Mass fraction of extractables, % - 0,45.

Example 7.

The experience is conducted under the conditions of example 6, but the number fed into the reactor, ethylene is 110 kg/h, the engine of the reactor serves 5 kg/hour, a Pressure in the reactor support 150 MPa, the residence time of the reaction mixtures in the upper and lower parts of the reactor is 50 (~25 in each part). The initiation of the polymerization reaction in the upper part of the reactor provide 10 wt.% a solution of tert-butyl peroxybenzoate in isododecane, at the bottom of the reactor 5 wt.% a solution of di-tert-butylperoxide in isododecane. The temperature of the reaction mixture in the upper part of the reactor is equal to 237oC, in the lower - 277oC, the temperature difference across the height of the reactor is ~40oC. the rate Constant for the decomposition of tert-butylperbenzoate at a temperature of 237oC - 6,7/s, the product of this quantity at the time of tert-butyl peroxybenzoate is 170. The rate constant of the decomposition of di-tert-butylperoxide at a temperature of 277oC - 9,6/s, the product of the rate constants for the dissolution of this peroxy of 18.4 wt.%, the total consumption of peroxide - 0,0019 mol per kg of polyethylene. Polyethylene has the following properties:

1. The melt flow index is 7.0 g/10 min.

2. The number of inclusions, PCs - 0.

3. Mass fraction of extractables, % - 0,45.

Examples 8-15 control carried out in conditions outside the claimed range of process parameters.

Example 8 (control).

The experience is conducted under the conditions of example 1, but the difference between the minimum temperature of the upper part of the reactor and the maximum temperature of the lower part of the reactor is 30oC, while the temperature of the polymerization reaction in the upper part of the reactor, measured by the first thermocouple, equal to 215oC, the second thermocouple - 247oC, as the initiator fed to the upper part of the reactor, use a solution of peroxides consisting of 5.6 wt.% tert-butyl peroxybenzoate and 4.4 wt.% tert-butyl peroxy-3,5,5-trimethylhexanoate, the rest of the solvent. The average temperature in the upper part of the reactor is equal to 231oC, the additive constant is the decay rate of the mixture of peroxides - 4,6/s, the product of the rate constants of decomposition of a mixture of peroxides during their stay in the upper part of the reactor is 150. In the lower part reativ fourth, the average temperature of ~238oC. To maintain this temperature in the lower part of the reactor serves 10 wt.%-s ' solution of tert-butyl peroxybenzoate in isododecane. The rate constant of the decomposition of tert-butylperbenzoate at a temperature of 238oC - 7,2/s, the residence time of the peroxide in the lower part of the reactor 15, the product of the rate constants of decomposition of tert-butylperbenzoate during his stay in the lower part of the reactor network 110. The conversion of ethylene in the experience is 15.5%, which is significantly lower than in the present method, the total flow of peroxides - 0,0025 mol per kg of the obtained polyethylene. Polyethylene has the following properties:

1. The melt flow index of 0.25 g/10 min.

2. The number of inclusions, PCs - 0.

3. Mass fraction of extractables, % - 0,49.

Example 9 (control).

The experience is conducted under the conditions of example 1, but the temperature difference between the minimum temperature of the upper part of the reactor and the maximum temperature of the lower part of the reactor is 80oC, while the temperature of the polymerization reaction in the lower part of the reactor, measured fourth thermocouple equal to 300oC. At this temperature in the reactor periodically explosion occurs is a measure 1, but the minimum temperature of the reaction mixture in front of the first thermocouple support 200oC, the temperature difference between the upper and lower parts of the reactor is 75oC. At this temperature occurs periodically explosive decomposition of the reaction mixture.

Example 11 (control).

The experience is conducted under the conditions of example 1, but the minimum temperature in the upper part of the reactor opposite the first thermocouple support 250oC, and opposite second thermocouple 262oC. the Average temperature in the upper part of the reactor - 256oC. the rate Constant of the decomposition of a mixture of peroxides consisting of 4 wt.% tert-butyl peroxy-3,5,5-trimethylhexanoate and 6 wt.% tert-butyl peroxybenzoate, equal to 24/s, the product of the rate constants of decomposition of this mixture during her stay in the upper part of the reactor is 790. The process of synthesis of polyethylene is unstable temperature, in the experience of say the increased consumption of initiators (0,0031 mol per kg of polyethylene), and the resulting polyethylene has a high content of extractable substances (0.71 wt.%).

Example 12 (control).

The experience is conducted under the conditions of example 6, but the number fed to the reactor ethylene). The product of the additive constants of the decay rate of the mixture of peroxides, tert-butyl peroxy-3,5,5-trimethylhexanoate and tert-butyl peroxybenzoate, supplied to the upper part of the reactor at the time of their stay in it, is equal to 120, and the product of the rate constant of the decomposition of di-tert-butylperoxide during his stay at the bottom of the reactor 260. The process of synthesis of polyethylene in these conditions are characterized by a higher consumption of peroxides (0,0040 mol per kg of polyethylene), low productivity (14 kg/h of polyethylene) and increased (to 0.65 wt.%) the content of extractable substances in the polyethylene.

Example 13 (control).

The experience is conducted under the conditions of example 6, but in the reactor serves to 1100 kg/h of ethylene. In this flow the residence time of the ethylene in the reactor is 5, and the product of the additive values of the rate constants for the decomposition of a mixture of peroxides during their stay in the upper part of the reactor is equal to 8, the corresponding value for the lower part of the reactor is equal to 18. In the experience occurs periodically explosive decomposition of the reaction mixture at the site of recycling high pressure caused by leakage of undecomposed peroxide from the reactor to the separation system of polyethylene from ethylene.

Example 14 (control).


1. The melt flow index is 3.0 g/10 min.

2. The number of inclusions, PCs - 2,0.

3. Mass fraction of extractables, % - 0,55, i.e. the number of inclusions and mass fraction of extractable substances polyethylene is substantially inferior to the polyethylene obtained in the inventive range.

Example 15 (control).

The experience is conducted under the conditions of example 6, but when the pressure of the synthesis of 270 MPa. Properties of the obtained polyethylene:

1. The melt flow index is 0.28 g/10 min.

2. The number of inclusions, PCs - 0.

3. Mass fraction of extractables, % - 0,45, i.e., the polyethylene does not have significant advantages, but the energy cost of compressed ethylene is substantially higher than it was when the polyethylene in the present conditions.

Example 16 (control, similar to the patent of Russian Federation N 1838330).

The experience carried out with the setup described in example 1, but one zone of the reactor is converted into dual-zone installation on the shaft of the agitator baffle which divides the reaction space into two zones - upper and lower. The upper area covers 56% of the total reaction space, the bottom is 44%.

In the reactor serves divided into three flow Atego space of the motor housing in the upper zone of the reactor. The second stream of ethylene in the amount of 4500 kg/h is injected together with the peroxide to the top of the reaction zone in front of the first thermocouple. As the peroxide in the upper area using 20 wt.%-s ' solution of tert-butylperoxybenzoate in dodecane. The amount of peroxide to the upper zone govern by the first thermocouple, maintaining a constant temperature of 172oC (445). In the second probe set temperature 197oC (470 K). The average temperature in the upper zone ~185oC, the rate constant of decomposition at this temperature for tert-butylperoxybenzoate is 5.7/s, the residence time in the upper zone 46, the product of the rate constant of decay of the specified initiator at the time of his stay in the upper zone is 260. The reaction mixture of the upper zone through the vent enters the lower zone of the reactor, which additionally serves to 5000 kg/h of fresh ethylene and opposite the third thermocouple to 1.2 wt.%-s ' solution of di-tert-butylperoxide in dodecane. The amount of initiator regulate fourth thermocouple. On the fourth thermocouple keep the temperature 270oC (543 K). On the third thermocouple is located under the vent, set the temperature of 232oC (505). The average temperature in the lower zone is 251Yes in the lower zone - 17, the product of these values is equal to 36. The total flow of peroxides was 0,0051 mol per kg of the polyethylene, the conversion of ethylene to 17.5 wt.%, the performance of 1750 kg/H. the resulting polyethylene has the following properties:

1. The melt flow index of 0.3 g/10 min.

2. The number of inclusions, PCs - 0.

3. Mass fraction of extractables, % - 0,69, i.e. significantly higher than in the polyethylene obtained in terms of the proposed method.

Example 17 (control, similar to the prototype).

The experience is conducted under the conditions of example 1, but as the initiator of the use of tert-butyl peroxybenzoate, supplied to the upper and lower parts of the reactor. Temperature process for the synthesis of polyethylene the following: the temperature of the reaction mixture in front of the first thermocouple - 230oC, opposite the second - 258oC, opposite the third - 238oC, opposite the fourth - 268oC. the temperature Difference between the minimum temperature in the upper part of the reactor and the maximum at the bottom is 38oC, average temperature in the upper part of the reactor 244oC, in the lower - 253oC. the rate Constant for the decomposition of tert-butylperbenzoate at these temperatures is 13/s and 20/s, respectively; the time of stay is esperantina during his visit to the upper part of the reactor is equal to 440, for the bottom 300. The consumption of peroxide - 0,0028 mol per kg of polyethylene. The conversion of ethylene to this mode is 17.1 per cent, which is considerably lower than in example 1, upon receipt of the polyethylene with the same melt flow index. The resulting polyethylene has the following properties:

1. The melt flow index of 2.0 g/10 min.

2. The number of inclusions, PCs - 0.

3. Mass fraction of extractables, % - 0,63, i.e. significantly higher than in the polyethylene obtained in terms of the proposed method.

Example 18 (control, similar to the prototype).

The experience is conducted under the conditions of example 1, but as the initiator of the use of tert-butyl peroxy-3,5,5-trimethylhexanoate supplied to the upper part of the reactor, and tert-butyl peroxybenzoate, served in the lower part of the reactor. Temperature process for the synthesis of polyethylene the following: the temperature of the reaction mixture in front of the first thermocouple - 220oC, opposite the second - 248oC, opposite the third - 245oC, opposite the fourth - 258oC. the temperature Difference between the minimum temperature in the upper part of the reactor and a maximum at the bottom is 38oC, average temperature in the upper part of the reactor 234oC, in the lower - 251o<-butylperbenzoate at 251oC - 19/C. the residence Time of tert-butyl peroxy-3,5,5-trimethylhexanoate at 234oC is 5.7/C, tert-butylperbenzoate at 251oC - 19/C. the residence Time of tert-butyl peroxy-3,5,5-trimethylhexanoate in the upper part of the reactor 33, tert-butyl peroxybenzoate in the lower part of the reactor 15 C. the product of the rate constants of decomposition of tert-butyl peroxy-3,5,5-trimethylhexanoate during his visit to the upper part of the reactor is equal to 190, the corresponding value for tert-butyl peroxybenzoate, used in the lower part of the reactor equal to 280. The total flow of peroxides - 0,0020 mol per kg of polyethylene. The conversion of ethylene in this mode, 16.4%, which is significantly lower than in example 6 upon receipt of the polyethylene with the same melt flow index. The resulting polyethylene has the following properties:

1. The melt flow index - of 0.30 g/10 min.

2. The number of inclusions, PCs - 0.

3. Mass fraction of extractables, % - 0,65, i.e. significantly higher than in the polyethylene obtained in terms of the proposed method.

As can be seen from the above data, the inventive method provides a higher conversion of ethylene, reduction of peroxides and getting polyethylene over you is of polyethylene by polymerization of ethylene in weight in one zone autoclave reactor with a mixing device at an elevated temperature, the pressure of 150-250 MPa and residence time of the ethylene in the reactor 10-50 with initiating the polymerization reaction of organic peroxides, supplied in the form of solutions in organic solvent in the upper and lower part of the reactor, and the subsequent two-stage separation of the obtained polyethylene from unreacted reaction mixture in systems recyclo high and low pressure, characterized in that the polymerization process support the difference between the minimum temperature value in the upper part of the reactor and the maximum value of the temperature in the lower part of the reactor in the range of 40-70oWith, in the upper part of the reactor set minimum temperature 215-240oWith, and in the lower part of the reactor maximum temperature 260-290oWith the top and bottom of the reactor serves the solutions of organic peroxides or solutions of mixtures of organic peroxides with these temperatures the value of the works of the rate constants for the decay of individual peroxide or additive constants of the decay rate of the mixture of peroxides during their stay at the top or bottom parts of the reactor, equal 16-240.

 

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EFFECT: increased degree of blowing and improved balance between hardness and fissuring resistance.

3 cl, 2 tbl, 5 ex

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